The present invention relates to a production management system for managing a production line including automatic machines such a robots for machining or installing parts on workpieces supported on carriages.
One recent production line system for manufacturing automobiles includes self-propelled carriages for delivering workpieces under the control of a controller and a plurality of work stations which are supplied with type data relative to the workpieces for enabling working robots at the work stations to install parts on the workpieces.
In such a production line system, it is necessary to supply correct processing instructions that match the type of the workpieces supported on the carriages that have arrived at the respective work stations. To meet such a requirement, Japanese Laid-Open Utility Model Publication No. 61-127921 discloses a system which supervises the movement of workpieces to work stations and displays on a display unit information about parts to be installed on a workpiece that has arrived at a work station which is attended by an operator and also information about parts to be installed on those workpieces which precede and follow the workpiece.
The above conventional system is however only aimed at improving the visibility of the information about parts to be installed by the operator at the work station, so that operation failures will be prevented.
Another known system disclosed in Japanese Laid-Open Patent Publication No. 61-249251 includes workpiece-supporting pallets which include thereon respective identification indicia. Information about processing details with respect to workpieces supported on the pallets can be accessed by reading the identification indicia of the pallets.
With this system, however, information about processing details with respect to a workpiece becomes available only when a pallet carrying that workpiece arrives at a work station. Therefore, a time required to prepare for the processing of the workpiece results in an operator standby time or a machine downtime or standby time and hence the production efficiency is lowered.